1. Field of the Invention
The present invention relates to an antenna and more particularly, to a wide receiving range antenna, which comprises a plurality of tubular resonators of different diameters for receiving signals of different frequencies.
2. Description of the Related Art
Following population of the Internet, fast development of communication and single-chip system technology, and diversification of communication service content, diversified high-tech products have been continuously developed and appeared on the market. It is the market tendency toward the realization of light, thin, short and small products with reliable and long life. In early time, an antenna was designed for receiving wireless signal of a specific frequency. Therefore, different antennas were necessary for receiving signals of different frequencies. In order to save the cost, multi-frequency antennas are developed. FIG. 8 shows a multi-frequency antenna according to the prior art. According to this design, the multi-frequency antenna comprises a holder base A, a coaxial cable A1 fastened to the holder base A, and a metal wire conductor B connected to the coaxial cable A1. The metal wire conductor B comprises a first coil portion B1 and a second coil portion B2 connected in series for receiving signals of different frequencies. This design of multi-frequency antenna has drawbacks. Because the metal wire conductor B has a first coil portion B1 and a second coil portion B2 connected in series, the antenna requires much installation space in an electronic device (for example, wireless exchanger or wireless network card). Because this design of multi-frequency antenna requires much installation space, it does not meet the technology necessary for the realization of light, thin, short and small products with reliable and long life. Further, it is complicated to process the first coil portion B1 and the second coil portion B2 subject to designed specifications, and the metal wire conductor B of the multi-frequency antenna may be deformed or damaged easily during delivery.
In order to eliminate the aforesaid drawbacks, a dual-frequency antenna is disclosed using two spaced hollow tubes to produce a high frequency signal resonance during a low frequency signal resonance. However, the performance of this design of dual-frequency antenna is still not perfect during a high frequency application.